feat: 진행 중인 채팅 조회 시에 timeAgo 필드 추가

Author: StoneCAU

src/main/java/shinhan/click/domain/chat/dto/response/ChatPreview.java

@@ -2,20 +2,49 @@
 
 import shinhan.click.domain.chat.entity.Chat;
 
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.time.temporal.ChronoUnit;
+import java.util.Locale;
+
 public record ChatPreview(
         Long chatId,
         String characterImageUrl,
         String characterName,
         String storyTitle,
-        String lastChat
+        String lastChat,
+        String timeAgo
 ) {
     public static ChatPreview from(Chat chat) {
         return new ChatPreview(
                 chat.getId(),
                 chat.getCharacter().getCharacterImageUrl(),
                 chat.getCharacter().getName(),
                 chat.getCharacter().getStory().getTitle(),
-                chat.getMessages().get(chat.getMessages().size() - 1).getContent()
+                chat.getMessages().get(chat.getMessages().size() - 1).getContent(),
+                getTimeAgo(chat.getMessages().get(chat.getMessages().size() - 1).getCreatedAt())
         );
     }
+
+    private static String getTimeAgo(LocalDateTime createdAt) {
+        LocalDateTime now = LocalDateTime.now();
+        long days = ChronoUnit.DAYS.between(createdAt.toLocalDate(), now.toLocalDate());
+
+        if (days == 0) {
+            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("a h:mm")
+                    .withLocale(Locale.KOREA);
+            return createdAt.format(formatter);
+        } else if (days == 1) {
+            return "1일 전";
+        } else if (days < 30) {
+            return days + "일 전";
+        } else if (days < 365) {
+            long months = days / 30;
+            return months + "개월 전";
+        } else {
+            long years = days / 365;
+            return years + "년 전";
+        }
+    }
+
 }